Translate the elements of a dataframe

The second beginner question. I want to create a new dataframe, where
each element of the original dataframe is translated to 1 if it was "+",
to 0 if it was "-" to -1 otherwise. I could do with:

Lines <- "a ? ?b ? ?c ? ?d
? ?+ ? ?- ? ?+ ? +
? ?+ ? ?+ ? ?+ ? -
? ?+ ? ?1 ? ?- ? '+ '
? ?- ? ?+ ? ?+ ? +
? ?+ ? ?N ? ?- ? +"


DF <- read.table(textConnection(Lines), header = TRUE)
cnames <- colnames(DF)
nrow <-length(rownames(DF))

nc <- length(cnames)
NDF <- data.frame(matrix(c(rep(0,nc*nrow)),ncol=nc))

for (i in 1:length(cnames)) {
?NDF[,i] <- sapply(DF[,i],function(x) if (x=="+") {1} else {if (x=="-")
{0} else {-1}} )
}
colnames(NDF) <- cnames

But this is shure one loop too much. Please give me the R way solution.